Full Idea
The original position is presented by Rawls as modelling the sense in which citizens are to be understood as free and equal.
Gist of Idea
The original position models the idea that citizens start as free and equal
Source
report of John Rawls (A Theory of Justice [1972]) by Adam Swift - Political Philosophy (3rd ed) 3 'Strikes'
Book Reference
Swift,Adam: 'Political Philosophy (3rd edn)' [Polity 2014], p.133
A Reaction
In other words, Rawls's philosophy is not a demonstration of why we should be liberals, but a guidebook for how liberals should go about organising society.